The U.N.’s humanitarian chief warned Tuesday that tens of thousands more people could be forced to flee Syria if Islamic State militants continue to make territorial gains.

Valerie Amos told the U.N. Security Council that during the past two weeks, Islamic State fighters have advanced in the northern Syrian city of Aleppo, causing more than 160,000 people to flee to Turkey.

She said most of those escaping were women and children who in many instances crossed heavily mined fields to seek safety. Amos warned that the number of refugees and internally displaced could grow significantly if ISIL - as the group also is known - continues unchecked.

“There is a possibility that tens of thousands more people could be forced out of Syria, if ISIL forces continue to gain ground,” she said.

Limited access

Amos made her remarks to the Security Council on the progress of the delivery of humanitarian aid in Syria, where distribution has been severely hampered by the government and armed groups.

She said nearly 11 million Syrians require urgent assistance. In August, the World Food Program and its partners were able to deliver food for about 4 million people.

Two months ago, the Council ordered the delivery of aid across Syria’s borders, with or without the government’s permission. Amos said that has helped humanitarians reach a few hundred-thousand additional people.

But she warned that despite $1 billion in humanitarian pledges for Syria and its neighbors, the U.N. and its partners are facing life-threatening funding gaps.

“Without additional funds, the World Food Program will be forced to end its operations completely within two months," she said.

"Rations have already been cut in order to continue to reach as many people as possible.”

Power speaks up

Speaking to reporters about the U.S.-led air strikes against ISIL targets in Iraq and Syria, Ambassador Samantha Power said Britain had just conducted its first strikes in Iraq. She added that the United States never asked for permission from the Assad government in Syria to carry out the strikes, but merely informed it of the intention to do so.

“We have concluded, and I think it’s very plain for everyone to see, that the Syrian regime cannot and will not take on ISIL in a manner that would deny this monstrous terrorist movement the safe havens that they have enjoyed in Syria for some time,” she said.

Ambassador Power said that in parallel with the strikes, the U.S. is helping to equip and train Syria’s moderate opposition, who she said has been fighting Islamic State militants at great personal expense and sacrifice.